Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

122
FXUS63 KLOT 221151
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
651 AM CDT Fri May 22 2026

.KEY MESSAGES...

- Chance of showers east of Interstate 57 overnight.

- Isolated to widely scattered showers and storms possible
  Saturday night into Sunday, though many areas will remain dry.

- Above normal temperatures expected next week.

&&

.DISCUSSION...
Issued at 226 AM CDT Fri May 22 2026

Surface high pressure in eastern Canada will keep fairly quiet
conditions over the forecast area today. Winds will remain out
of the northeast and high temperatures are expected in the mid
60s north of Interstate 80, low 70s south of the Interstate, and
upper 50s/low 60s along the immediate lakeshore. A parent upper
level short wave currently analyzed over the northern Plains is
expected to lift northeastward through the day toward the
Minnesota Arrowhead through the overnight into Saturday
morning. A second southern impulse wave is expected to lift from
the lower Mississippi Valley toward southeast Michigan. There
is still some uncertainty on the exact track of this wave, but
model guidance has been showing good continuity in having the
core of the wave (and the reflected surface low) focus its path
through central Indiana (east of our forecast area). While there
is a slight chance for some northwestward development, highest
chances remain east of Interstate 57 in northwest Indiana.
Instability with this wave remains non-zero and forcing appears
fairly weak and it is expected to pass over the area in a
unfavorable time of day. An isolated thunderstorm is possible,
better chances remain east of the forecast area. Lastly,
steering flow aloft with this wave is fairly weak (thus leading
to slow storm motions). At the risk of sounding like a broken
record, the higher modeled QPF is expected east of the area, but
still around or just over an inch of precipitable water is
forecasted in northwest Indiana. If a stronger shower were to
develop, slow storm motions would increase the concern for
downpours and localized flooding. For now, considering models
are focused east of the area, this remains a low confidence
threat, but certainly one to monitor in the overnight.

As the wave exits Saturday morning, drier conditions over the
area can be expected during the daytime hours. Midlevel winds
will turn to the west-southwest allowing for warmer temperatures
to advect in, nudging afternoon high temperatures into the 70s
across much of the forecast area, though still cooler at the
lakeshore due to onshore flow.

The parent upper level wave will slowly move east over the
western Great Lakes Saturday night through Sunday. Isolated to
widely scattered showers and storms may pass over the region
Sunday. Forcing looks weak with this wave as well, and while it
does not look favorable for severe weather, the best chances for
storms appears to be south and east of Interstate 55. Coverage
of storms could be impacted by the speed of the wave. There are
some models that have this wave passing east of the area by
early afternoon.

An upper level ridge is expected to build early next week
keeping the forecast dry for not just Memorial Day but through
the early part of next week. 850 mb temperatures start reaching
15C with chances surface temperatures climb above normal into
the low to mid 80s early next week. Models are showing the
potential for another upper level trough to approach the area
midweek that could provide the next chance for precipitation.

DK

&&

.AVIATION /12Z TAFS THROUGH 18Z SATURDAY/...
Issued at 651 AM CDT Fri May 22 2026

Key aviation forecast messages:

- MVFR to near IFR CIGs develop late evening-early Saturday AM.

- A period of rain may occur overnight for part of the area (30%
  chance at GYY). Confidence in the western extent remains low
  (20% chance at ORD/MDW).

East to northeast winds are expected through the period around
15 kt during daylight hours with occasional lower 20 kt gusts.
An expansive but thin ~4000-6000 ft cloud layer remains
overhead this morning. This may scatter out later this morning
before filling back in late afternoon ahead of our next weather
system lifting toward the region. Expect gradually lowering
ceilings thereafter through the evening and overnight hours to
MVFR and potentially near IFR. Guidance has trended a bit
farther northwest with the area of showers tonight into early
Saturday morning. Opted to introduce a PROB30 at GYY to account
for this. Have held off for the Chicago area TAF sites for now
but a precip mention may become warranted if this trend
persists, including the potential for associated MVFR
visibilities and IFR ceilings.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement through Saturday afternoon for ILZ006-
     ILZ103-ILZ104.

IN...None.
LM...Small Craft Advisory until 4 AM CDT Saturday for the IL
     nearshore waters.

&&

$$

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